Tatra T-813 8x8 Kolos

[Sariel]

LEGO Tatra trucks are dime a dozen, but whenever I see them, they are either very large, complex and sluggish, or they are small but don't really have the unique Tatra suspension, nor drivetrain, nor steering. So I set out with a simple goal: make the smallest Tatra model I can that has it all: the suspension, drivetrain and steering just like in the real Tatra truck. This is the result:

 

[Zerobricks]

It looks really great with the studded chassis, custom wheels and the small details.

While it does look good, I think mechanically-wise you could improve the functions:

• Redesign the driveline so the driveshaft doesn't also bear the weight and suspension forces of the truck
• Increase gear ratio on half axle to reduce torque flex/sway of the truck
• Steering sytsem looks weak (pinballs can fall out) and the wheel angles are affected by suspension travel, since steering and suspension points do not coincide. Real tatras use a different steering setup with steering links placed almost parallel to the chassis to minimize affect of suspension on steering angles.

[Sariel]

I think exactly neither of these is doable at this scale. Also, towballs aren't going to fall out from force being applied at right angle to them. There is simply no force pulling them out.

[Zerobricks]

Just now, Sariel said:

I think exactly neither of these is doable at this scale. Also, towballs aren't going to fall out from force being applied at right angle to them. There is simply no force pulling them out.

I beg to differ:

 

[Sariel]

Just now, Zerobricks said:

I beg to differ:

Respectfully, what you're showing there looks much wider than T-813. I'd say possibly as much as 20% wider. My model has been carefully scaled to the same wheels (I only put custom tires on later) and it's over 2 cm narrower, the axles even more.

[jorgeopesi]

The steering and the suspension axle point are not aligned, so when lowering the suspension the technic links will move one wheel to the left and another to the right, have the real Tatras the same issue?, I would like to see how they solve it. I hate the wheels but this will be always my problem.

Edited June 29, 2018 by jorgeopesi

[Sariel]

The steering links are aligned with the suspension arms, so I think you're exaggerating. You can see the suspension working in the video and no such effect occurs.

[HorcikDesigns]

Please read this as reaction from man, who really likes Tatras, built many of them from LEGO, and was really looking forward to see experienced builder's attempt at building another Tatra truck. 
It has stunning chassis, which makes me wonder whether it is still LEGO, good tire choice, really interesting video, nice body that in some spots screams for more details (windshield), but the thing that I really do not like  is the horribly monstrous (in this scale) fake engine, that looks like something violently crammed inside the cab and the steering wheel, that looks odd.
 It might have been a nice scale model, with decent performance, but that engine willfully sitting in the cab, that is slightly disproportional (?) and needs some more angles here and there, leaves me slightly disgusted and disappointed. Sorry. 

Building Tatra truck is difficult, and you did awesome job with it, but I prefer looks to the functions. 

Edited June 29, 2018 by HorcikDesigns

[jorgeopesi]

You can try it, when the wheels stay in the position of your awesome video there is no problem but if you move the wheels up or down the steering will be affected without touching the steering wheel, of course it is a minimum steering issue. I solved it in my tatras by lifting the drive shaft above the steering links.

[Sariel]

The engine is certainly somewhat oversized, but its location is pretty close to the real thing, so I don't know why this is such a problem. As for the windshield, I would definitely love to use one in there, but since the top of the cabin is 14 studs wide, I would need two 7-studs wide windshields. As you know very well, LEGO doesn't make anything like that.

Edited June 29, 2018 by Sariel

[suffocation]

Brilliant model, both in looks and functions.

I'm amazed at how well it handles rough terrain - the suspension is hypnotising.

[pagicence]

@jorgeopesi the issue you are talking about only occurs when you are using Ackerman geometry in Lego models. Whether that occurs in real life on actual Tatras I don’t know. Because you can’t see that from videos you really need to be up-close in person to witness it. In this model Sariel does not use Ackerman geometry, so that issue is not present.

@Sariel you only failed to do the actual Tatra steering system. In your video @1:07 the steering linkage and its connections and the Ackerman geometry are clearly shown. My guess is that it couldn’t be replicated in such small scale. Everything else is good.

@Zerobricks you did recreate Tatra steering system as it is real, but you are getting counter Ackerman geometry in your models. The point where you connect steering arms (towballs) to the front axle should be in front of the axle. In your case they are behind the axle thus giving you counter effect turning the outer wheel more inward then the inner wheel. But nice solution. As for the drive shaft not to bear the load you would need to build the truck in 1:5 scale to achieve that. Because on the real truck the driveshaft itself is incased in protective tubing as its seen @1:00 and @1:03 of the video. Hell that’s not possible to build even in 1:10 scale. And your lime and purple truck does not have the pivot point for the half axles on the center driveshaft, so you are wrong in this particular case.

Believe me when I say this people, I studied this closely for my MOCs.

Edited June 29, 2018 by pagicence

[sirslayer]

hey, can we say that all of their ideas are good and that what makes Sariel MOC and everyone MOC unique different .  Great model Sariel !!!   

[pagicence]

Absolutely. Both MOCs are great. And the ideas behind them. There is no doubt about it.

[jorgeopesi]

You never knows so I built it and you can see the result. One wheel to the left and another to the right when the suspension is not compressed, I think the steering never have to be affected for the suspension travel. I love Tatras and I have fought a lot against this problem.

 

 

[Hogwartus]

I don't think it all is a problem unless it affects model's performance, which is great.

Excellent model @Sariel.

[Sariel]

Actually, in my model the steering links don't really overlap, so they are wider. I just kept the animation in my video simple for clarity (sorry for the confusion). See below:

Edited June 29, 2018 by Sariel

[Johnny1360]

Looks good, I personally like these smaller scale models, it often seems more challenging to keep all the proper functions and still make it look right. 

Are those tires the RC4WD ones that rm8 reviewed last month? I really like the looks of them but I am on the fence about buying some. How do you like them, work out okay? 

[jorgeopesi]

2 hours ago, Sariel said:

Actually, in my model the steering links don't really overlap, so they are wider. I just kept the animation in my video simple for clarity (sorry for the confusion). See below:

I know it I only explain the concept, I expent hours watching real Tatras and I think that they have the same small issue.

[Leonardo da Bricki]

Impressive model @Sariel! I am amazed yet again by the solutions in this model for the drivetrain and axles. Extremely well done for the scale.

Only minor thing is that I also think the model would be fine with a scaled static engine; as cool as the working one is, it just looks out-of-place.

Edited June 30, 2018 by Leonardo da Bricki
Curse of Misspelling was cast...

[Sariel]

8 hours ago, Johnny1360 said:

Are those tires the RC4WD ones that rm8 reviewed last month? I really like the looks of them but I am on the fence about buying some. How do you like them, work out okay? 

They're excellent, just a little hard to clean and much, much grippier than LEGO tires, which should be kept in mind when building performance models.

[nerdsforprez]

Really enjoy your builds Sariel, and this one is no different.  Filled with examples for non-experts like myself to learn from, and looks are pristine and accurate. 

One issue that I am not so sure of however, is the speed of the vehicle.  I know in the intro. you mentioned how you tire of slow tatras, but in real life, especially when they are climbing or going through difficult terrain, they are slow. In all your models you really strove for accuracy, looks-wise it is very accurate.  But no one would drive that fast over the terrain showed in the video.  Vehicle looks choppy not like a lot of fun to drive.  At least my perception when watching you drive it was that you had to be very careful and hyper-aware.  Probably could have used some down-gearing, or at least progressive throttle, so it was not so jerky.

[HorcikDesigns]

19 hours ago, Sariel said:

The engine is certainly somewhat oversized, but its location is pretty close to the real thing, so I don't know why this is such a problem. As for the windshield, I would definitely love to use one in there, but since the top of the cabin is 14 studs wide, I would need two 7-studs wide windshields. As you know very well, LEGO doesn't make anything like that.

...

I did not complained the position, only the scale.
About the windscreen, I did not meant adding some glass, only some bars that would respect the slope of real thing. Your current version is strictly vertical.
It is awesome-looking MOC, with ideas made nearly to perfection, but some things could be done better, IMHO. :) 
(I have to consider trying to reverse-engineer this chassis, the springs work almost flawlessly) 

Edited June 30, 2018 by HorcikDesigns